Wireless tuning system



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Application filed July 9, 1921.

To all whom it may concern Be it known that l, PARKER E. Wreem, a citizen of the United States, and a resident of Vi/ilkinshurg, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Wireless Tuning Systems, of which the following is a specification.

My invention relates to radio receiving systems, and more particularly to a system for coupling thermionic amplifiers to the antenna circuit to obtain regenerative arnplificationc An object of my invention is to accomplish regenerative amplification by employin a thermionic am liiier not onl having a tuned plate circuit to effect regenerative amplification hut also employing an inductive coupling" between the plate and grid circuits to give a direct feed-hack.

A further oloiect of my invention is to varythe regenerative effect by varying; the capacitance of a bypass condenser shunted around a high reactance device in the plate circuit of a receiving tube.

A still further o oject or my invention is to simultaneously vary the tuning of the plate circuit and the size of the lay-pass condenser shunting the high reactance device, whereby, in receipt oi energy of long wave-lengths, "more radio-frequency current may pass than in the receipt of energy of short wave-len a'ns.

Heretofora where direct ed-haclr by inductive coupling" has heen provided hetween the plate and grid circuits of vacuum tuhes operating as receivers, wave distortion has resulted. lilo-rec er, when feedback inductance devices were employed, theadiustment of the inductance in the plate circuit to the desired value to furnish the correct amount of feed-hack has neon a diii'icult prololem. Where a tuned plate circuit alone has been employed, it has not heen an easy matter to ohtain sufficient regeneration. for the reason that the degree of feed-leach depends upon the sharpness of tuning. A received wave of a length dih ering very slightly from the resonant wave-length often made the regenerativeaction too My receiving system comprises antenna circuit includine an inductance device, across the ends of which is conductively connected the grid circuit oi a three-electrode vacuum-tir s. iii device i erine" with WIGGrIl T, @1 1 VHLKI'WSBURG, EENNSYLVAIQIA, ASSIGNQR T0 WESTING- IVZANUFAGTURING GOllKPANY, A CORPORATIUN 01" PENNSYL- in the plate circuit of the vacuum tube is inductively coupled to the antenna inductance device, which is, as above outlined, common to the grip circuit of the tube. varying the variable inductance in the plate circuit of the tube, the plate circuit may be brought into resonance with the received frequency.

There is a regenerative amplification which takes place by reason of the tuning" or" the plate circuit of the tube, the inter nal reactance of the tube serving as a feedback coupling between the grid the plate circuits.

Shunted around a high reactance device in the plate circuit, which in the present instance comprises a plate battery and the primary winding" of an audio-frequency transformer. is an adjustable icy-pass condenser. The lay-pass condenser allows radio-frequency current to pass hv the high reactance device, and the means for adjustingthe hv-pass condenser and varying; a tuning inductance in the plate circuit of the tuhe are so connected that, when the wave length is increased, the capacitance of the icy-pass condenser is simultaneously increased. This arrangement permits oi great steadiness in the operation of the tuhe, with simplicity of adjustment, since in practice it is necessary that more radiofreouencvcurrent flow in the plate circuit at the longer wave-lengths. in order to maintain a proper feed-haclr coupling.

The single figure of the drawing is a diagrammatic view illustrating a receiving" system etinhodying the principles of my invennon.

in the drawing, l have shown an antenna circuit comprising an antenna 1, a variable condenser 2 and a variometer 3, whence the circuit is connected to ,around. The means for varying: the variahle condenser and the variometer are linked together so that capacity and inductance are increased simultaneously. therehy insuring" that the curve representing capacity and inductance shall he a straight line. However, they may he separately variaicle without interhe hinctioningr of my system.

-@onduetivelv connected to the antenna circuit around the ends of the varionieter 3 is the grid circuit of an electron tube 4, operating as a regenerative amplifier and a element 5 a plate element 6 and a filament element 7 the latter being heated by means of a suitable battery 8. In the lead to the grid is located a grid condenser 9 shunted by a grid leak resistance 11, performing the well understood function of maintaining the grid 5 at a suitable negative potential, although it is to be understood that positive grid potentials may be maintained on tubes which operate best with a positive bias on the grid.

In the plate circuit of'the tube 4 is located a variometer 12, a plate battery 13 and the primary winding 14 of an audio-frequency transformer 15. The plate battery 13 and the transformer windin 14 are shunted by a variable by-pass con enser 15. The. variometer 12 and by-pass condenser 15 are mechanically connected for simul taneous adjustment ,in such manner that when the tuning of the plate circuit is changed for a longer Wave-length, the capacitance of the by-pass condenser 15 will be increased to allow the passage of more radio-frequency current around the highreactance elements comprising'the plate battery 13 and the winding 14. The variometers 3 and 12 are provided with shields. 16 and 17 respectively.

In inductive relation to the primary winding 14 of the audio-frequency transformer is a secondary winding 18 which is connected in series with a telephone receiver 19.

In operation the antenna circuit comprising the antenna 1, the variable capacity 2 and the variometer inductance 3 is tuned to the frequency of the waves which it is desired to receive. The grid circuit of the electron tube 4 is conductively connected around the variometer 3, and the potential of the grid 5 of the tube 4 is caused to vary in accordance with the received oscillations, while the grid is maintained at a suitable negative value by the grid condenser 9 shunted by the grid leak resistance 11. The tube is adjusted to operate as a regenerative amplifier which necessitates a certain degree offeed-back between the plate and grid circuits.

In my system. I furnish the necessary feed-back for the regenerative action by means of the tuning of the plate circuit to resonance at the received frequency. The

I plate battery 13 and the transformer winding 14 constitute a high impedance to the passage of radio frequency current, and the by-pass condenser 15 offers a path of relatively low impedance, whereby suflicient radio-frequency current may pass to insure eflicient regenerative action.

I have found that the feed-back coupling, I

if'adjusted for relatively short wave-lengths, is not sufficient for eflicient regenerative action at longer wave-lengths unless special precautions are taken. I therefore provide a mechanical connection between the variometer 12 and the variable by-pass condenser 15, whereby an increase in the variometer inductance to increase the wave length 1s accompanied by an increase in the capacitance of the variable by-pass condenser 15. By increasing the capacity of the by-pass condenser, I increase the feed-back coupling without resort to variable inductive coupling, thereby greatly simplifying the adjustment. Theflow of the lowfrequency component of the plate current through the primary winding 14 induces oscillations in the secondary winding 18,.and these may easily be detected in the telephone receiver 19.

I claim as my invention: 7

1. In an oscillatory-current system, the combination with a main circuit carrying oscillatory currents of a predetermined frequency, of an amplifier having controlling and controlled circuits, means for coupling one of said amplifier circuits to said main circuit, and means for tuning to resonance the other of said amplifier circuits in su h manner that the currents traversing the same increase as the wave length thereof increases.

2. In an oscillatory-current system, the combination with a main circuit carrying oscillatory currents of a predetermined frequency, of an amplifier having controlling and controlled circuits, means for coupling one of said amplifier circuits to said main circuit, means for tuning to resonance the other of said amplifier circuits, a device having a relatively high impedance connected in said last-mentioned circuit, and a variable-impedance by-pass circuit connected across said high-impedance device and common means for so adjusting said tuning means and the impedance of said bypass circuit that the impedance of said bypass circuit decreases as the impedance of said tuning means increases, whereby the regeneration of said system may be -increased.

'3. In an oscillatory-current system, the combination with a main circuit carrying oscillatory currents of a predetermined frequency, of an amplifier having controlling and controlled circuits, means for coupling one of said amplifier circuits to said main circuit, means'for tuning to resonance the other of said amplifier circuits. a device having a relatively high impedance connected in said last-mentioned circuit, a variable-impedance by-pass circuit connected across said high-impedance device, and com mon means for simultaneously tuning said last-mentioned amplifier circuit and for ad justing the. impedance of said by-pass circu'it.

4. In a'regenerative system including an amplifier having controlling and controlled circuits, tuning means whereby both of said circuits may be caused to carry currents of the same-frequency, whereby a regenerative feed-back coupling may be obtained through theinterna-l impedance of said amplifier, a device having a relatively high impedance connected in one of said circuits and a variable-impedance by-pass circuit connected across said high-impedance device, the method of varying the wave-length without materially varying the efiiciency of the regenerative operation, which consists in simultaneously varying the tuning of said circuits and the impedance of said by-pass circuit in such manner that said impedance decreases as the wave-length increases.

5. In an oscillatory-current system, the combination with an amplifier having magnetically coupled controlling and controlled circuits, of means for tuning said controlled circuit to cause effective feed-back coupling within said amplifier, one of said circuits including a device having high impedance to oscillatory currents, a variable by-pass condenser across said impedance, and means actuated by said tuning means foradjusting said by-pass condenser to increase the action of the magnetic coupling at low frequencies.

6. In an oscillatory-current system,- the combination with an amplifier having controlling and controlled .circuits, means for providing a feed-back coupling between said circuits, means fortuning one of said circuits, a device having a relatively high impedance to oscillatory currents connected in said last-mentioned circuit, a variable bypass condenser connected across said highimpedance device, and common means for simultaneously tuning said last-mentioned circuit and for adjusting the impedance of said by-pass condenser.

7. In a regenerative system including an amplifier having controlling and controlled circuits, means for providing a feed-back coupling between said circuits and for tuning the same, a device having a relatively high impedance to oscillatory currents connected in one of said circuits, and a variable by-pass condenser connected across said high-impedance device, the method of varying the wave-lengths without materially varying the efliciency of the regenerative operation, which consists in increasing the capacitance of said condenser as the wavelengths are increased. and vice versa.

8. 'A receiving system comprising an antenna circuit. a thermionic amplifier having input and output circuits, 'an inductor for tuning said output circuit to efiect regenerative amplification, a high-impedance device in the output circuit and an adjustable byass condenser for radio-frequency currents iiridging the high-impedance device, and common means for adjusting said inductor and said condenser, whereby the degree of regeneration may be maintained independent of the operation of said tuning inductor.

9. The combination of a threeelectrode vacuum tube operating as a regenerative amplifier and having input and output cir cuits, a device ofiering a high impedance to currents of radio frequency connected in the output circuit. a variable by-pass condenser for radio-frequency currents shunting said high-impedance device whereby the degree of regeneration may be varied, and means operated by tuning the output circuit to long wave length for increasing the capacity of said condenser.

10. A receiving system comprising an antenna circuit, an amplifier having input and output circuits, a high-impedance device in the output circuit, an adjustable by-pass condenser for radio-frequency currents bridging the high-impedance device and means for tuning the output circuit to resonance at different frequencies and for simul taneously adjusting the bypass condenser in such manner that. at longer wave lengths more radio-frequency current may pass.

11. In an amplifier system, a vacuum-tube device having input and output circuits, a variable inductance in the output circuit loosely coupled to the input circuit, whereby the output circuit may be tuned with but little change in said coupling, thereby establishing regenerative action within the tube, said output circuit also including a source of power and an impedance, and a condenser shunted around said source and impedance and means for adjusting the capacity of said condenser to increase the current through said output circuit atlong wave lengths.

12. The combination with a three-electrode vacuum tube, of an input circuit, an output circuit. a loose electromagnetic coupling between said circuits. means. including one element of said coupling, for tuning said output circuit. whereby regenerative action will occurboth in said coupling and within the tube. an adjustable condenser in said output circuit constituting a part of said tuning means, and a high-impedance device and a source of power in shunt to said condenser whereby, at longer wave lengths, said output circuit will carry larger current.

In testimony whereof, I have hereunto subscribed my name this th day of June,

PARKER E. WIGGIN. 

